Neuro-surgical therapy is a technique that can be used to treat an aneurysm, i.e., a sac shaped localized enlargement of the cross-section of a patient's artery. During neuro-surgical therapy, a clip is typically used to clamp off the aneurysm from the blood circulation. Neuro-surgical therapy can decrease the likelihood of the aneurysm rupturing.
To determine whether the aneurysm sac has been completely closed with the clip and whether the blood flows properly in other arterial vessels in close proximity to the clip, a fluorescent dye can be administered intravenously to the patient and the flow of the dye into the artery can be observed through a camera. If the blood mixed with the fluorescent dye is visible in the aneurysm sac, this indicates that the aneurysm sac was not completely closed with the clip. Similarly, if the blood mixed with the fluorescent dye is not visible in certain regions of the artery until after a delay, this can indicate that those regions of the artery are least partially blocked.